This invention relates to a composition of matter, a method and an article of manufacture. More specifically, the subject invention is directed to a photosensitive composition which readily undergoes selective alteration in its physical and/or chemical properties upon image-wise exposure to activating electromagnetic radiation. The photosensitive composition can be readily formed, independent of binders, into films or adherent coatings useful in the graphic arts and in the manufacture of circuit boards for the electronics industry.
The use of photosensitive films and coatings in both the graphic arts and in the manufacture of circuit boards is well known. Typically, the composition of such films and coatings can include a polymeric constituent, which may itself be photosensitive, and a sensitizer composition. Upon selected exposure of this film or coating to imaging energies, the photosensitive species within the composition would either itself undergo a degradative reaction or promote degradation of one or more of the other components of the composition. It is, of course, readily appreciated that such degradative reaction is only of value in such a system where it is essentially confined, or limited, to those areas of the composition impinged upon by such imaging energies. The concept of "degradation" as used throughout this disclosure is contemplative of any photoinduced alteration or shift in one or more of the physical and/or chemical properties of the composition. The image thus created within the film or coating can then be "developed" by selective removal of the exposed components of the film or layer which have been subjected to imaging energies. The ability to create such selective degradative changes in films and coatings prepared from a photosensitive composition has been appreciated for some time. The basic difference in the various approaches in the formulation of such photosensitive compositions has been in the search for a system which is prepared from relatively inexpensive ingredients, does not require prolonged imaging cycles (has a high quantum efficiency) and results in the creation of high resolution images within the composition which can be manifested without prolonged and elaborate development.
The various mechanisms for selective photodegradative changes in photosensitive polymeric films and coatings include:
(a) hydrogen extraction from a polymer backbone by a photosensitive species as disclosed in U.S. Pat. No. 3,964,907; PA1 (b) acid catalyzed depolymerization of a degradable polymer as disclosed in U.S. Pat. No. 3,917,483; and PA1 (c) oxonium ion-induced cleavage of a degradable polymer as disclosed in U.S. Pat. No. 3,923,514. PA1 (a) a polymer component comprising a plurality of structural units of alkyl aryl ethers which are end-capped with a substituent functional group containing an ethylenically unsaturated moiety, and PA1 (b) a photosensitizing effective amount of a free radical generating compound for example those selected from the group consisting of benzophenone, benzil, benzoin, acetophenone, thioxanthone, anthraquinone and the substituted analogues thereof. PA1 (a) self-condensation of an alkyl aryl ether; PA1 (b) condensation of two or more alkyl aryl ethers; or PA1 (c) condensation of an alkyl aryl ether with paraformaldehyde. PA1 Z=H.sub.2 or .dbd.O PA1 V=halogen PA1 R.sub.3 is selected from the group consisting of: ##STR6## where q=0 to 3; and M is an aromatic radical selected from the group consisting diaryl aliphatic, diaryl ethers, diaryl sulfides, diaryl sulfones, diaryl amines, diaryl ketones and diaryl diketones; and PA1 R.sub.4 =R.sub.3 PA1 G=X or Y PA1 R.sub.7 =R.sub.4 when S=X or is absent when S=Y PA1 m=1 to 3 PA1 p=1 to 8 PA1 Y=--CH.sub.2 OCH.sub.2 -- PA1 X=--CH.sub.2 --
All of the foregoing references disclose the application of one or more of the above mechanisms to the selective photodegradation of photosensitive compositions containing formaldehyde, or an aldehyde linkage.
It is an object of this invention to provide a novel polymeric photosensitive composition having enhanced mechanical and physical properties.
A further object of this invention is to provide a novel polymeric photosensitive composition wherein the photodegradable polymer component thereof is of sufficient molecular weight to form a tough adherent film or coating with or without binders.
Still yet a further object of this invention is to provide a novel polymeric photosensitive composition which has improved mechanical and physical properties, and which can be readily developed by simple contact with an alkaline solution.